Former U.S. Open champion, Sloane Stephens, qualifies for first WTA finals

Stephens, 25, won her first Grand Slam title at Flushing Meadows in 2017, but was knocked out in the quarter-finals by Anastasija Sevastova this year.

She also reached the final at the Australian Open, Internazionali BNL d'Italia and the Western & Southern Open.

Simona Halep is back as the year-end No. 1 for the second year in a row, despite a back injury that doctors say could lead to a long-term problem.

"I haven't practised 100 per cent yet but today, tomorrow, I will do close to 100", Halep said in a conference call, "and I will be able to know better the next day".

The world's number one, who has already qualified for the WTA year-ending finals, added that she chose to play in Moscow to solve the problems that she still experienced after the back injury before playing at Singapore.

"Finishing the season as the WTA world number one a year ago was a huge honour for me", said Halep.

"If I can't play here, I'm very doubtful that I will be able to play in Singapore". She has been at the top of the rankings for nearly the entire year even though her results had suffered as the season wore on.

Stephens joins Romania's Simona Halep, Germany's Angelique Kerber, Denmark's Caroline Wozniacki, Japan's Naomi Osaka and the Czech Republic's Petra Kvitova who have already secured a spot in the tournament.

The WTA Finals will see the world's best players vie for a total prize money of US$7 million ($9.65 million) and two of the most prestigious titles in women's tennis.

With momentum on her side, Garcia broke Pliskova's serve twice to claim her first WTA title since her back-to-back triumphs in Wuhan and Beijing a year ago. "To do it for a second time in 2018 feels like a special achievement, especially having also won my first Grand Slam this year".